Posted Under: Sustainable Landscapes

Churches - A Big Stormwater Footprint

Large Buildings and Large Infrequently Used Parking Lots

Church properties provide a great opportunity for sustainable landscape practices to be used. With a large building footprint creating enormous amounts of runoff any available green space should be considered for capturing, or minimally filtering, stormwater. This can be done with rain gardens/bioswales, underground stormwater storage chambers and/or rainwater harvesting systems (large of course) and permeable pavements in the people-traffic areas.

Another big ticket, is the parking lot. Churches have a unique scenario of needing a lot of parking space - infrequently. Most of the time when you drive by a church during a weekday there's a few cars, once a week things are fairly full and then wow the big events, packed. How does a designer design for this? Historically parking lot designs are done with those big events in mind but rethinking this scenario is vital for the health of our watersheds. What about sizing the pavement for the often used circumstance based on say a 6 month analysis and then using alternative pavements for the higher use needs. These areas are often referred to as overflow parking and various alternative pavement types, such as a turfstone, or a grid structure filled with soil and turf, could be used. Of course instituting capture facilities like rain gardens planted with native plants where any stormwater off the parking lot drains towards is a smart thing to do.

Approaching a stormwater mitigation retrofit (or new construction) should start with a purpose in mind, say a 5-year, 24-hour rain event which in Minneapolis/St. Paul currently is 3.5" of rain. Factoring that runoff from impervious areas and knowing the subsoils then helps to define things. Certainly poor infiltrating soils will cause bigger expenses so being realistic is important. Even minimally thinking about filtering runoff using most importanly native plants is doing something rather than nothing.

One last consideration and budget-friendly is to think of decreasing pavement with sharing resources. Why not partner with potential neighboring properties that need parking during the week but not on the weekends? Cities are becoming less structured with parking codes because this issue of stormwater quality requires property owners to take big steps towards change. Plus with more intense rain events, city stormwater infrastructure is over-burdened and the impact on our waterways extreme.

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